The Captain folded his brow into a look of intense perplexity. 'You seem exceedingly spry for a man who demolished an entire bottle of brandy and better part of an ounce of shag in a single evening.'
'And very nice too,' said the tramp. 'Now as to breakfast?'

From Middle Englishshaggen, from Proto-Germanic*skakkōną(“to shake”), specifically continuing a post-Proto-Germanic variant *skagg-, where the non-singular stem *skag- caused the analogical replacement of the stem-final voiceless geminate consonants with voiced geminates, which was then leveled throughout the paradigm.

They were in the midst of an intense snog, his tongue down her throat as he tried to work out if he wanted another shag before she left for the night, when an odd noise sounded from behind the door of 2B.

'It turned out that it was me who was just a shag to him. He had a girlfriend I didn't know about. He presumed I was up for some no-strings action. And the thing is, I thought I was – in theory. But in practice, I realized that I wasn't.'

I'm fcuked then mate. Born and bred sarf london and the missarse is a brummie. Oh and her old man is a scouser!!¶ You all still sound like a bunch of inbreds though but it's better than the Hereford accent "alright shag where you be"

2010, Featherstone, John, Hangman's Got The Blues:

I was going down the stairs to get my bike when I ran into Jim Mudd coming up. "Alright shag?" he said like we were best mates.

2015 February 18, “Not had a fag for weeks”, in Reddit‎[5], r/TheRedLion: